Method and Apparatus for Correcting Errors in a Multiple Subcarriers Communication System Using Multiple Antennas

1. A method for spatial multiplexing (SM) transmission using multiple antennas in a wireless access system, the method performed by an apparatus and comprising: performing a first transmission using a first precoding matrix for the SM transmission; and performing a second transmission using a second precoding matrix to have a smaller spatial multiplexing rate than the first transmission, wherein the second precoding matrix is consist of at least one column of the first precoding matrix, and wherein a number of the at least one column corresponds to the smaller spatial multiplexing rate.

2. The method according to claim 1 , wherein the second precoding matrix is selected based on a precoding matrix index received from a receiver.

3. The method according to claim 1 , wherein the first transmission is performed using two codewords, and the second transmission is performed using one codeword.

4. The method according to claim 3 , wherein the second transmission is a retransmission of the first transmission.

5. The method according to claim 1 , wherein the first and the second transmission are open loop SM transmissions.

6. An apparatus configured for spatial multiplexing (SM) transmission using multiple antennas in a wireless access system, the apparatus comprising: the multiple antennas; and a controller for supporting the SM transmission, wherein the controller controls: the multiple antennas to perform a first transmission using a first precoding matrix for the SM transmission; the multiple antennas to perform a second transmission using a second precoding matrix to have a smaller spatial multiplexing rate than the first transmission, wherein the second precoding matrix is consist of at least one column of the first precoding matrix, and wherein a number of the at least one column corresponds to the smaller spatial multiplexing rate.

7. The apparatus according to claim 6 , wherein the second precoding matrix is selected based on a precoding matrix index received from a receiver.

8. The apparatus according to claim 6 , wherein the first transmission is performed using two codewords, and the second transmission is performed using one codeword.

9. The apparatus according to claim 8 , wherein the second transmission is a retransmission of the first transmission.

10. The apparatus according to claim 6 , wherein the first and the second transmission are open loop SM transmissions.